1. Field of the Invention
The present invention relates to an information recording medium, an information recording method and an information recording/reproduction system, in which it is possible to increase the reliability of data recording by dynamically extending the spare area according to the frequency of occurrence of defective sectors.
2. Description of the Related Art
An optical disk is a type of information recording medium which has a sector structure. In recent years, as the recording density and the capacity of an optical disk have been increased, it has become more important to ensure the reliability thereof.
Conventionally, a defect management method is known in the art for managing defective sectors on the optical disk (i.e., sectors which cannot be used for recording/reproduction of data). A spare area is provided in advance on the optical disk. When there is a defective sector on the optical disk, the defective sector is replaced by another sector in the spare area. Thus, the reliability of the optical disk is ensured. Such a defect management method is described in International Standards Organization ISO/IEC 10090 for 90 mm optical disks.
The conventional defect management method described in the International Standards Organization ISO/IEC 10090 for 90 mm optical disks will now be outlined with reference to FIGS. 12 and 13.
FIG. 12 illustrates a structure of a data recording area 800 of a conventional optical disk.
The data recording area 800 includes a plurality of sectors. Each of the plurality of sectors is assigned a physical sector number (hereinafter, referred to as a “PSN”).
The data recording area 800 includes a defect management information area 801, a spare area 802 and a volume space 800a. The volume space 800a is arranged immediately after the spare area 802, and is defined as an area in which user data can be recorded. Each of the sectors included in the volume space 800a is assigned a logical sector number (hereinafter, abbreviated as an “LSN”).
The size of the spare area 802 is predetermined. In order to change the size of the spare area 802, it is necessary to change the data structure of the replacement information stored in the defect management information area 801 by using a special command with physical format utility software. This operation will hereinafter be referred to as an initialization operation.
FIG. 13 illustrates a procedure of a conventional format operation and a conventional data write operation. These operations are performed by a system control apparatus and an optical disk drive apparatus. The optical disk drive apparatus is connected to the system control apparatus. The system control apparatus is, for example, a computer system.
The format operation includes steps S901–S903 illustrated in FIG. 13. The data write operation includes steps S904–S911. In FIG. 12, each reference numeral that starts with “S” beside an arrow denotes a recording operation corresponding to a step illustrated in FIG. 13.
When an optical disk is inserted into the optical disk drive apparatus, the optical disk drive apparatus reads out the defect management information area 801 and recognizes replacement information which indicates that a defective sector has been replaced by a spare sector (step S901).
The system control apparatus performs a FAT/root directory creation operation, issues a Write command and transmits data to the optical disk drive apparatus (step S902).
The optical disk drive apparatus uses format utility software to recognize the physical structure of the optical disk and records the data transmitted from the system control apparatus from the beginning of the volume space 800a (step S903). As a result, a FAT area 803 and a root directory area 804 are arranged starting from the beginning of the volume space 800a. Such a logical format operation is similar to the format operation for a file system in a MS-DOS format. As a result, the area from immediately after the root directory area 804 to the end of the optical disk is handled as a file data space 800b which is managed by the FAT.
A data write operation for recording data (File-a) under the root directory will now be described.
The system control apparatus performs a recording operation for the data (File-a), issues a Write command and transmits data to the optical disk drive apparatus (step S904). The location at which the data should be recorded is specified by an LSN.
The optical disk drive apparatus records the data transmitted from the system control apparatus in a sector which is assigned the specified LSN (step S905). Whether or not the data has been correctly recorded is determined by reading out the recorded data and by comparing the read data with the transmitted data. When the data has not been correctly recorded, the sector which is assigned the specified LSN is detected as a defective sector. The defective sector occurs mainly due to dirt or dust attached to the optical disk.
For example, assume a case where sector b (sector 814) illustrated in FIG. 12 has been detected as a defective sector. In such a case, the optical disk drive apparatus records the data which is supposed to be recorded in the defective sector 814 in #1 spare sector 810 of the spare area 802, generates, as defect management information, #1 replacement entry 832 which indicates that the defective sector 814 has been replaced by the #1 spare sector 810, and records the #1 replacement entry 832 in the defect management information area 801 (step S906).
The #1 replacement entry 832 includes location information 833 indicating the location of the defective sector and location information 834 indicating the location of the spare sector by which it is replaced. Each of the location information 833 and 834 is represented by a PSN.
When the system control apparatus instructs the optical disk drive apparatus to read out data from the defective sector 814, the optical disk drive apparatus performs address conversion with reference to the #1 replacement entry 832 and reads out the data from the #1 spare sector 810.
Thus, by replacing a defective sector by a spare sector, it is possible to ensure the reliability of the optical disk. Moreover, since such defective sector replacement operation is performed by the optical disk drive apparatus, it is possible to ensure that the system control apparatus always records data at a location corresponding to the specified LSN. As a result, the system control apparatus can handle the optical disk as a defect-free medium.
Then, the system control apparatus performs a root directory recording operation, issues a Write command and transmits data to the optical disk drive apparatus (step S907).
The optical disk drive apparatus updates root directory information recorded in the root directory area 804 according to the data transmitted from the system control apparatus (step S908).
The system control apparatus performs a FAT recording operation, issues a Write command and transmits data to the optical disk drive apparatus (step S909).
The optical disk drive apparatus updates FAT information recorded in the FAT area 803 according to the data transmitted from the system control apparatus (step S910). Thus, the data (File-a) is registered under the root directory.
The optical disk drive apparatus records the updated defect management information in the defect management information area 801. Such recording is performed when there is no data recording instruction from the system control apparatus for a few seconds.
In the above-described conventional defect management method, the size of a spare area is fixed. Therefore, if there occurs defective sectors beyond the size of the replacement area, data cannot be recorded on the optical disk even when an unallocated area available for recording still exists on the optical disk. In order to record data on the optical disk, it is necessary to change the size of the spare area by performing another initialization operation on the optical disk. In such a case, data recorded in the volume space needed to be backed up on another medium before performing the initialization operation because the LSN allocation would be changed over the entire area of the volume space.
Especially, in a case where an optical disk is used with consumer equipment, the user may handle the optical disk while eating food or a child may inadvertently touch the surface of the optical disk, whereby more defective sectors may occur on the optical disk than expected by the manufacturer.